In recent years, with an object of shortening processes related to mounting methods of semiconductor chips, the use of pre-applied underfill film (PUF) wherein an underfill film is applied to electrodes of an integrated circuit (IC) has been investigated.
Packaging methods using this pre-applied underfill film are, for example, performed in the following manner (For example, refer to PTL 1).
Step A: An underfill film is applied to a wafer and the wafer is diced to obtain a semiconductor chip(s).
Step B: The semiconductor chip is aligned on the substrate after the application of the underfill film.
Step C: The semiconductor chip and substrate are thermally compressed together, electrical conduction is ensured using metallic bonding of solder bumps, and the semiconductor chip is bonded to the substrate by curing of the underfill film.
Since the pre-applied underfill film is used after lamination on a wafer in advance, the melt viscosity thereof is set to be low in order to achieve an excellent solder connectivity for packaging on a substrate. For example, most of the conventional underfill films have a storage modulus G′ of 10E+04 Pa or less and a loss modulus G″ of approximately 10E+03 Pa and they do not exhibit non-Bingham fluidity in a molten state, so that removal of air during packaging tends to be insufficient, thus creating voids in a packaging body.